With the recent increase in the amount of information to be stored in magnetic disk devices, there is a requirement for higher recording density with such devices. In the case of a thin-film magnetic head caused to fly over a magnetic disk surface for recording information on the recording medium and reproducing the recorded information, therefore, the flying height of the head above the disk surface should be reduced in order to increase the recording density. In order to achieve a reduction in the flying height of the magnetic head, it is necessary to enhance the precision and accuracy of shaping in the production of a slider for the head.
Conventionally, the processing of a slider material to produce a slider for a thin-film magnetic head has been carried out by mechanical working or machining. However, in view of the requirement for higher precision as well as complicated shape including a curved surface, etc., the mechanical working or machining processes are limited in accuracy and, therefore, development of a new fabrication process has been desired. Namely, mechanical working or machining can form substantially straight shapes only, and cannot provide a rail shape comprising a curved line or complicated combination of straight lines necessary for obtaining a stable and small flying height of the magnetic head. The recent target value for the head flying height is 0.1 .mu.m or below, the achievement of which requires a negative pressure type slider or rails having portions of curved shape.
Besides, in order to cause a thin-film magnetic head to fly stably with a gap of about 0.1 .mu.m between the head and a magnetic disk surface, accurate finishing of the rail width is required. In the case of a rail width of several hundreds of micrometers, for example, the variation of finished size must be within a few .mu.m. In this point, also, the mechanical working or machining processes have come to be limited in application to the slider shaping.
As a method of forming a rail shape which cannot be obtained by mechanical working or machining, there have been proposed a method of processing a slider material by sandblasting through a mask, and a method of evaporating a surface portion of the slider block by scanning with a laser beam. Although these proposed methods can produce quite complicated rail shapes, the methods are still unsatisfactory as to finishing accuracy of rail width, with variations in the finished size being 10 .mu.m or more. Therefore, these methods have not reached a sufficient technical level for practical use.
In order to overcome the above difficulties and provide a process for forming a freely selected rail shape with high accuracy, studies have been made of the use of an organic polymeric material for a dry-etching mask through utilization of photolithographic techniques commonly used in wafer processes for semiconductor fabrication, as for example described in Vacuum, Vol. 38, No. 11, pp. 1007-1009 (1988). The dry etching process (hereinafter referred to simply as "dry process") using such photo-process has made possible a shaping with higher accuracy, as compared to mechanical working or machining, and without generating strains. However, magnetic-head sliders are formed generally from a difficultly processable material, such as titanium oxide, alumina, etc., and dry etch selectivity for the slider material relative to the mask material is low; accordingly, formation of a deep cut into the slider material requires a greater mask-material thickness. In practical fabrication of a slider, the mask thickness must be not less than several tens of micrometers, taking into account the etch selectivity for the slider material. On the other hand, the requirement for accuracy in finishing the slider rail width is very rigorous as described above. Consequently, the uniformity of film thickness of the mask material is an important factor.
When a thick film of a mask material is formed by, for example, roll coater printing, screen printing or the like, there is a tendency toward cracking of the thick film or toward nonuniformity of film thickness. In addition, air bubbles are liable to be entrained in the film surface, leading to unsatisfactory finishing accuracy. Furthermore, it is advantageous, from the viewpoint of throughput, to carry out the slider shaping for a plurality of wafer blocks, because side faces of the blocks cut from a wafer after the wafer process for fabrication of magnetic heads are to be processed. However, due to the presence of gaps between adjacent ones of a group of wafer blocks being processed simultaneously, such film-forming methods as spin coating are in many cases not applicable.
U.S. Pat. No. 4,226,018 discloses a method for manufacturing a floating type thin film magnetic head wherein a thin metallic film which has been patterned is placed on a magnetic head core block and the core block is ion etched for producing slider rails. However, the dimensional accuracy of such resultant slider rails is insufficient for the shaped slider rails for several reasons including the fact that the metallic thin film cannot be perfectly adhered to the surface of the core block material resulting in dimensional inaccuracies and that the previously patterned metallic film cannot be accurately positioned with respect to the surface of the core block on which it is placed and cannot be used for some desired shapes of rails.